[Security] Bump symfony/dependency-injection from 2.8.11 to 2.8.50

[dependabot-preview]

Bumps symfony/dependency-injection from 2.8.11 to 2.8.50. This update includes security fixes.

Vulnerabilities fixed

Sourced from The PHP Security Advisories Database.

CVE-2019-10910: Check service IDs are valid

Affected versions: >=2.7.0, <2.7.51; >=2.8.0, <2.8.50; >=3.0.0, <3.1.0; >=3.1.0, <3.2.0; >=3.2.0, <3.3.0; >=3.3.0, <3.4.0; >=3.4.0, <3.4.26; >=4.0.0, <4.1.0; >=4.1.0, <4.1.12; >=4.2.0, <4.2.7

Commits

• c306198 security #cve-2019-10910 [DI] Check service IDs are valid (nicolas-grekas)
• a2f40df Bump phpunit XSD version to 5.2
• 8b7508c Skip empty proxy code
• bc5e7d8 [CS] Enforces null type hint on last position in phpDocs
• 8421939 Consistently throw exceptions on a single line
• 1607759 minor #28301 Fix code examples in PHPDoc (maidmaid)
• 01b722a [DI] Fix phpdoc
• 700bdb3 Fix code examples in PHPDoc
• 2b41cf2 [HttpKernel] Fix inheritdocs
• ad2446d Enable native_constant_invocation CS fixer
• Additional commits viewable in compare view

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[dependabot-preview]

Superseded by #460.